1. Field of the Invention
The present invention relates to a data transmission method, and more particularly, to an apparatus and method for data transmission for minimizing electromagnetic interference (EMI) occurring upon parallel data transmission. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for a data driving apparatus of a liquid crystal display.
2. Discussion of the Related Art
Nowadays, the amount of video data transmitted through a transmission medium has been increased to satisfy a user's demand on a high quality image. As a result, the video data has been transferred at a high speed. In an effort to achieve this end, a transmission frequency of the video data has been increased and the number of transmission lines for transmitting the video data has also been increased. As the video data having a high frequency is transferred synchronously over the increased data transmission lines, electromagnetic interference (EMI) occurs among the data transmission lines.
In order to reduce the EMI, the number of the data transition has been reduced in the liquid crystal display (LCD) by using a data modulation system. Alternatively, the transmission frequency has been reduced by using a six-bus system.
FIG. 1 shows a data driving apparatus of a conventional LCD that transmits video data by using a six-bus system.
Referring to FIG. 1, the data driving apparatus includes data driving IC's 8 for driving data lines of a liquid crystal display panel 10, and a timing controller 2 for controlling a driving of the data driving IC's 8. Each data driving IC 8 is mounted on a tape carrier package (TCP) 6 to be connected to the liquid crystal display panel 10. Further, each data driving IC 8 is connected to a timing controller 2 through the TCP 6 and a printed circuit board (PCB) 4.
More specifically, in the liquid crystal display panel 10, gate lines and data lines are arranged in such a manner to cross each other. Liquid crystal cells are positioned at every area where each gate line cross each data line. The liquid crystal display panel 10 is provided with pixel electrodes and a common electrode for supplying an electric field to each of the liquid crystal cells. Each pixel electrode is connected to one of data lines through source and drain electrodes of a thin film transistor as a switching device. The gate electrode of the thin film transistor is connected to one of the gate lines allowing a pixel voltage signal to be applied to the pixel electrodes for each line. Accordingly, the liquid crystal display panel 10 controls light transmittance by the electric field applied between the pixel electrode and the common electrode in accordance with the pixel voltage signal for each liquid crystal cell, thereby displaying a picture thereon.
The data driving IC's 8 apply a pixel voltage signal to each data line whenever a gate signal is applied to one of the gate lines by gate driving IC's (not shown). Particularly, the data driving IC's 8 convert digital video data (pixel data) inputted from the timing controller 2 into analog pixel voltage signals.
The timing controller 2 controls driving of the data driving IC's 8 and the gate driving IC's and applies the pixel data to the data driving IC's 8 at the same time. To this end, as shown in FIG. 2, the timing controller 2 includes a control signal generator 3 for generating control signals, and a data aligner 5 for aligning the pixel data in conformity to the six-bus system.
The control signal generator 3 generates data control signals (i.e., SSC, SSP, SOE and POL, etc.) for controlling the data driving IC 8 using a main clock signal MCLK and horizontal and vertical synchronizing signals H and V inputted from the exterior thereof. The data control signals are applied to the data driving IC 8 through each transmission line included in a data control signal bus 16. Further, the control signal generator 3 generates and supplies gate control signals (i.e., GSC, GSP and GOE, etc.) for controlling the gate driving IC (not shown) to the gate driving IC through a control signal bus (not shown).
The data aligner 5 aligns pixel data R, G, and B inputted from the exterior thereof in conformity to the six-bus system to supply to the data driving IC 8. In other words, the data aligner 5 divides the pixel data R, G, and B into even-numbered pixel data RO, GO, and BO and even-numbered pixel data RE, GE, and BE to simultaneously supply to the data driving IC 8 through each three odd-numbered data buses 12 and each three even-numbered data buses 14. Herein, when each pixel data RD, GD, and BD consists of a 6-bit signal, each of the odd-numbered data buses 12 and the even-numbered data buses 14 consists of 6 data transmission lines. Thus, the data buses include 36 data transmission lines in total.
The data driving IC of the conventional LCD transmit the pixel data by the six-bus system to reduce the transmission frequency, thereby reducing the EMI. However, the conventional data driving apparatus fails to reduce the EMI because the number of data transmission lines is increased.